Verifies that the specified checkbox is checked.

```js
I.seeCheckboxIsChecked('Agree');
I.seeCheckboxIsChecked('#agree'); // I suppose user agreed to terms
I.seeCheckboxIsChecked({css: '#signup_form input[type=checkbox]'});
```

@param {CodeceptJS.LocatorOrString} field located by label|name|CSS|XPath|strict locator.
@returns {void} automatically synchronized promise through #recorder
